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000
FXUS62 KGSP 201754
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
154 PM EDT Sat Apr 20 2024

.SYNOPSIS...
Much cooler temperatures and widespread light rain is expected
overnight into Sunday with drier weather returning by Monday. Warmer
weather returns by Tuesday and continues through the workweek.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 1230 PM EDT Saturday: Light returns continue across the NC
Piedmont this afternoon per the latest radar mosaic loops. However,
only isolated light rain is being reported within the band so most
of it is not making it to the ground. Nonetheless, introduced a
slight chance PoP across the NC Piedmont through the next few hours.
With cloud cover clear across much of the forecast area this
afternoon, especially NE GA and the SC Upstate, thus reduced cloud
cover further in these areas per the latest visible satellite loops.
Temps where there are mostly sunny skies, mainly NE GA and the SC
Upstate, have already climbed into the upper 70s and lower 80s. Max
temps will be nudged upward a few degrees the next update if mostly
sunny skies prevail.

Otherwise, the western Carolinas and northeast Georgia will remain
under a nearly-zonal flow through the near term that will have some
weak vorticity moving across the Southeast, but nothing significant.
The flat flow should allow for a weak cold front to lay down and
move south across the SC/GA part of the fcst area today and then
stall closer to the Gulf Coast tonight. Along this boundary, some
weak convergence will persist into the afternoon, enough so that a
few of the CAMs manage an isolated thunderstorm or two east of the
mtns. The RAP/GFS manage about 1000-1500 J/kg of sfc-based CAPE this
afternoon, but unlike yesterday, the effective shear is only about
25-35kt and from the west. So...not quite as favorable as
yesterday...when we saw the development of a few supercellular
storms east of the mtns...but still enough instability and shear to
support an mini-supercell-like storm or two...which the HRRR hints
about. Will include a small chance of storms and will also mention
the isolated severe storm chance in the HWO. Temps will not be as
warm as yesterday, but still on the order of five degrees above
normal. Any isolated convection will end with the loss of daytime
heating, and with that concluded, we will await the development of
isentropic upglide that should develop ahead of a broadly-defined
srn stream wave moving into the MS Delta region early Sunday. The
CAMs agree that light precip will develop/spread northeast into the
fcst area after midnight...to what extent remains a bit unclear.
Either way, we should be on our way to developing a cold air damming
wedge by daybreak Sunday. Overnight low temps will be about a
category above normal, but this should be one of those odd
situations when the calendar day high temp occurs right after
midnight, and the calendar day low happens late in the day.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 100 PM EDT Saturday: Rainfall directly associated with the
southern stream wave will pull away from the area Sunday evening
with just a small lingering pop early in the Piedmont areas. A
vigorous mid level trough will swing quickly through on Monday. This
system will have little moisture with which to work, so the main
impact will be just keeping conditions cooler than climo for Monday.
Flat mid level ridging and weak surface high pressure will be the
main weather influences for Monday night and Tuesday.

Temperatures Sunday night and Monday night will be cool with lows in
the 30s in the mountains and lower to middle 40s in the Piedmont.
Right now, it looks like temperatures will remain just above and
frost/freeze concerns in the mountain valleys, but this will need to
be watched closely. Highs Monday will be nearly 10 degrees below
climo warming to around 3 degrees below climo on Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 115 PM EDT Saturday: A mid level trough will move from the
Great Lakes into the Northeast for the middle of the week. This will
push a weak and mainly dry cold front into the area on Wednesday.
Mid level heights will quickly rebound from this trough for Thursday
and Friday. Another system will impact the area late in the week
with some showers possible by Friday, mainly in North Carolina.
Temperatures for the middle to end of the week should be pretty
close to climo.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Sfc high pressure will dominate through late
this evening leading to mostly dry conditions. However, isolated
thunderstorms may develop late this afternoon into early this
evening thanks to ample daytime heating. Thunderstorms look to
develop around/near KCLT, KGSP, and KGMU from roughly 21-24Z so have
introduced TEMPOs at these terminals. Could not rule out the
possibility of an isolated strong to severe storm impacting any of
the aforementioned terminals. Dry conditions will return around
sunset due to the loss of daytime heating. The rest of the terminals
should remain dry this afternoon and early evening. A few terminals
are reporting low-end gusts this afternoon; KAVL, KGMU and KAND.
Intermittent low-end gusts should stick around through this
afternoon before gradually diminishing this evening. The exception
will be KAVL where low-end gusts may linger through late this
evening before tapering off. Winds will start out W`ly across the SC
Upstate terminals early this afternoon before gradually turning N`ly
this evening. Winds will start out NW`ly at KHKY and KCLT early this
afternoon before gradually turning N`ly this evening. Winds east of
the mountains will gradually turn NE overnight and will remain NE
through Sunday. Winds will remain NW at KAVL through the entire 18Z
TAF period. Both restrictions and rain chances will return overnight
into early Sunday morning as in-situ cold air damming develops. Cigs
will gradually lower from west to east early Sunday morning becoming
IFR by late Sunday morning. -RA will linger through the end of the
18Z TAF period for all terminals thanks to isentropic ascent. No
thunderstorms are expected with stable cold air damming in place.
Cigs may lift to low-end MVFR levels early Sunday afternoon but
confidence on this is low at this time.

Outlook: VFR and dry conditions return Sunday night into early next
week as high pressure builds into the region from the west.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...SCW
NEAR TERM...AR/PM
SHORT TERM...SCW
LONG TERM...SCW
AVIATION...AR